The present invention relates to binder compositions and methods for curing such binder compositions. The binder compositions of the present invention are especially useful as molding compositions for refractories and abrasive articles, and for molding shapes such as foundry cores and molds. The binder compositions are capable of hardening at ambient temperatures.
Various binder systems now used, including binders for molding compositions employ inorganic substances as the major components.
The inorganic binder systems have generally been limited to the so-called "no-bake processes" where the binder, curing agent and aggregate are mixed and packed in a core box. Over a period of time the packed mixture hardens sufficiently so that it can be removed from the mold and allowed to harden further. Inorganic binder systems of this nature have a limited bench life since the curing agent begins to function immediately upon mixing. Although inorganic binder systems are available for use in the "cold-box process", such binder systems have met with only limited success. Cores made with silicate carbon dioxide systems usually exhibit low strengths and poor shake-out properties. The term "cold-box process" refers to the method of making foudnry cores, molds, etc., whenever a mixture of aggregate and binder are compacted into a core box and then contacted with a gaseous curing agent. Systems using organic binders such as benzylic ether resins, cured with gaseous amines are discribed in U.S. Pat. No. 3,404,579. A cold-box process system with improved shake-out in which inorganic binders mixed with aggregate are cured with a gaseous curing agent is highly desirable, particularly because less quantities of noxious gas would be liberated during the metal casting process.
A primary object of this invention is to provide inorganic binder systems which can be rapidly cured at room temperature by contact with a gaseous curing agent.
Another object of this invention is to provide inorganic binder systems having an extended bench life.
Still another object of this invention is to provide an inorganic binder system useful in "cold-box" core making processes.
Still another object of this invention is to provide an inorganic binder system having good removal or "shake-out" of the moulding shape from the metal casting.